1. Field of the Invention
The present invention relates to an apparatus for the separation of mixtures and is particularly useful in separating a fluid from a solid contained therein. The apparatus is well suited for the separation of blood plasma or serum from the blood cellular and particulate matter phase. In many laboratory and clinical situations, it is desired to separate a solid or semi-solid fraction of a mixture from a liquid fraction of the mixture. This may be accomplished in a number of fashions, with one of the most efficient being the use of an apparatus which is inserted into a sample containing tube to physically separate the liquid from the solid fraction of the mixture. The present invention provides such an apparatus which is capable of separating the liquid from the solid fraction of a mixture by the insertion of the apparatus into a sample containing tube. After the separation has been effected, a self-sealing portion of the apparatus is withdrawn from the sample containing tube as a contamination free, shippable container having the sample of the liquid collected contained therein. Remaining behind in the collection tube is the piston member which effectively seals the sample containing tube, providing a contamination free, sealed disposal means for the contaminating solid contained in the sample containing tube.
2. Description of the Prior Art
As is well known, the market place is replete with fluid separators, many of which are adapted to specialized purposes and useable only for those purposes. U.S. Pat. No. 3,586,064 shows an apparatus for the collection of blood wherein a hollow central body is closed at both ends by pierceable elastomeric seals. The seals are pierced by respective needles, so that when the device is inserted into a collection tube, one of the needles allows the liquid to flow into the interior of the hollow tube, while the other needle provides a vent to atmosphere. When sufficient sample has been collected, the atmosphere vent needle is withdrawn and the septum seals itself. Thereafter, the apparatus is withdrawn from the collection tube and the second needle is withdrawn, providing a self-sealing container for the collected sample.
U.S. Pat. No. 3,837,376 shows a similar apparatus wherein both ends of the collecting apparatus are exposed to the atmosphere while the liquid sample is being forced into the collection apparatus, but in this case, only one needle is used whereby the needle has two vents to be disposed within the interior of the collection apparatus. During the collection operation, liquid flows from the sample containing tube through the needle, into the hollow body through the lower one of the two vents. After the fluid has been collected in the lower portion of the collection apparatus, both ports are again free of fluid and atmospheric communication through the needle vents is established with the interior of the sample containing tube. This facilitates the removal of the collection apparatus from the sample containing tube without interference of so-called vacuum lock problems.
A similar device is shown in U.S. Pat. No. 3,983,037 wherein a flexible walled hollow tube, closed at both ends, is penetrated at one end by a needle-like structure. The end of the needle-like structure which terminates inside the collection apparatus is attached to a filter so that fluid passing through the needle-like structure from the sample containing tube is filtered before it passes into the interior of the collection apparatus. To employ this device, the collection apparatus is compressed to form a partial vacuum on the interior. The needle-like portion protruding from the closed end of the collection apparatus is inserted under the surface of the fluid to be collected, and the pressure on the collection apparatus is released, thereby causing the fluid in the sample containing tube to be drawn up into the needle, passed through the filter, and be collected on the interior of the collection apparatus.
U.S. Pat. No. 3,693,804 shows a pressure differential sampling device wherein the collection apparatus consists of a hollow body portion having one end closed by a piston filter assembly wherein a filter is fitted within a piston structure, and the piston filter structure is fitted within the hollow body of the collection apparatus. To employ the device, the assembly is forced into a sample containing tube so that the liquid is forced through the filter device into the interior of the hollow body portion of the collection apparatus. When sufficient sample has been collected, the collection apparatus is tilted sharply within the sample containing tube to break the seal therebetween and allow withdrawal of the entire apparatus.
In a similar device, U.S. Pat. No. 4,057,499, shows a blood collection apparatus comprising a hollow body tube having a piston member inserted into one end thereof. The piston member is generally bell-shaped with the narrowest portion of the bell structure being inserted into the hollow-body member. The piston contains a filter member through which passes fluid to be collected. In the upper end of the bell-shaped piston member is a one-way valve which allows the fluid to flow through the filter material and into the interior of the hollow body member of the collection apparatus. The composite piston member has a laterally extending flange which sealingly engages the interior wall of the sample containing tube while the collection apparatus is being forced into the sample tube to collect the fluid contained therein. Upon withdrawal of the entire collection apparatus, the flange of the piston folds over itself so that an upper radially grooved portion of the flange moves from its up position into a downward position, thereby breaking the seal between the flange member and the interior walls of the sample containing tube.
Many related fluid collection devices are known. For example, see U.S. Pat. Nos. 3,687,296, 3,850,174, 3,875,012 and 3,931,815.